1. Field of the Invention
The present invention generally relates to couplers for transmitting torque from a rotary drive mechanism to a rotary driven tool and, more particularly, is concerned with a torque transmitting coupler incorporating torque transmission, shear capability and component separation containment features.
2. Description of the Prior Art
It has long been the practice in the utility industry to drive screw anchors into the ground near utility poles to provide anchorage for guy wires and cables. A typical screw anchor is composed of an elongated rod having an eye formed on its upper end and a helix-shaped auger blade attached on its pointed lower end.
Tractor-mounted and hand-held devices are known which could be adapted for use in installing screw anchors into the ground. Representative of the prior art are the devices disclosed in U.S. Pat. Nos. 3,343,612 to Flowers, 3,961,671 Adams et al and 4,057,114 Anderson.
The preferred approach for installing screw anchors is to use the end of the same truck-mounted earth boring auger that was used to dig the hole for the utility pole. As disclosed in a U.S. Pat. No. 2,883,223 to Petersen, typically a screw anchor adapter is employed for coupling the anchor rod upper end to a pilot tip of the earth boring auger. The use of the utility truck-mounted earth boring auger as the driver for installing screw anchors into the ground has proven to be a relatively safe acceptable practice since a pushing force directed toward the ground is being employed. Should a screw anchor hit an obstacle and fracture while being set into the ground, the downward direction of the force being applied by the earth boring auger minimizes the possibility of components coming apart and causing damage or injury.
However, the same practice has not been allowed up to the present time for recovery or removal of screw anchors from the ground. To remove screw anchors a pulling force directed away from the ground must be employed. Should the screw anchor be hung up in the ground and fracture while being turned and pulled by the earth boring auger, the upward direction of the force being applied by the auger increases the possibility of components coming apart and flailing about so as to subject equipment and persons nearby to damage and injury. As a result, present practice to recover a screw anchor has been to drill holes with the earth boring auger or with a back hoe on either side of the anchor in order to loosen it and dig it out. This is time-consuming and required replacement of the soil removed once the anchor is removed.
It is still perceived that a utility truck-mounted earth boring auger is the most desirable and practical drive mechanism to use in removing screw anchors. Torque overload protective couplers and adapters have been disclosed over the years in the prior patent art, such as in U.S. Pat. Nos. 2,819,635 to Better et al, 3,735,625 Fabrizio et al, 4,086,012 Buckley et al and 4,447,217 Blandford. However, none of these devices appear to provide suitable low-hazard means to connect the earth boring auger to a screw anchor for removal of the same. Consequently, there still exists a pressing need to devise a way to eliminate the hazards associated heretofore with use of the utility truck-mounted earth boring auger in such manner.